“Damian’s death was planned since the beginning,” said Grant Morrison in an interview with Kevin Smith on Fat Man on Batman. In the interview, Morrison stated that Damian was going to appear in only one arc. However, the fans really liked the character so he stood for a while. After six years, Grant Morrison wants to end the story the way he planned all along, leaving his mark on the Caped Crusader.
To hear the full interview: Fat Man on Batman